EP 1152921 describes a searchlight arranged for being mounted on e.g. a helicopter, in which said searchlight by means of two motors is arranged for being rotated up and down with respect to a vertical plane, but is limited to shining from the horizontal, to downwards to the almost vertical. From the EP patent applications' column 2 line 22 is cited: “In the side view of the preferred embodiment of the lighthead (2), the adjustable extension range θ of the lighthead (2) is shown. Preferably, the adjustable extension range θ of the lighthead (2) is between approximately 0 degrees and approximately 120 degrees, and more preferably is approximately 80 degrees.” This makes said searchlight unsuitable as a searchlight on a ship, as such a searchlight must be able to shine upwards with respect to the deck plane during roll movements and pitch movements at sea, which the EP patent can not perform when it is mounted on board a ship. The patent does not describe a method for adjusting the position of said searchlight with respect to the vessels roll- and pitch movements.
U.S. Pat. No. 3,979,649 describes logic circuits for commanding a searchlight from two different command consoles, but does not provide a solution to the problem to be addressed towards an object or point in the sea.
DE 20207444 is a German utility model which describes a searchlight which allegedly, without furnishing any constructive details or algorithms, furnishes a system which is supposed to be arranged for keeping said searchlight directed towards the same geographic location independently of said vessels location and inclination. Page 3 second paragraph describes the following:
“Through collection of measurement data (of ship velocity and course, and roll, pitch, and roll measurements and data analysis, the electromagnetic drive gears of said searchlight are thus controlled in such a manner as for keeping the searchlight cone directed towards this location, and completely without the operating person having to furnish further control signals.” In the German utility model several essential elements which would be necessary for the implementation of the desired method as described are however lacking. Firstly the German utility model does not take into account said searchlights height above the sea level, or height or placement with respect to the vessels main axes. Said height is a completely vital parameter which must be known to be able to maintain said searchlight directed towards a point in the sea which distance initially is unknown. If said searchlights elevation above the axis-centre of the boat is not taken into account, it will not be possible to compute said searchlights' movement if said vessel is subjected to pitch or roll movements, and thus said searchlight will not be able to keep the light directed towards the same point in the water. For searches e.g. from helicopters, knowing the elevation is essential. Secondly the searchlight according to the German utility model does not compensate for said vessels' heave movement. Such a heave movement is always present to a larger or lesser degree. It is of cardinal importance to compensate said searchlights movement with respect to said vessels heave movement, especially if the illuminated object is situated a long distance from said searchlight. Thirdly, the German utility model does not take into account said searchlights location on said vessel with respect to said vessel main axes. Especially for roll movements this will be critical, as said searchlight may be arranged high up and to the side of said vessels mass centre. Furthermore there will be a large influence on the beam axis point of intersection with the sea surface if said searchlight is arranged far forward or aft in said vessel and said vessel has a large pitch movement. Thus the placement of said searchlight is a completely essential parameter which must be taken into account if the searchlight is to compensate for the movements of said vessel. If this is not taken into account, said searchlight must be arranged in said vessels mass centre, i.e. the centre of said vessels rotational movement about its three main axes for the angle calculations of the compensation of said searchlights for said vessels movement to be correct. This is not practically feasible. Thus the German utility model only compensates for pitch, roll and yaw, whereas the present invention compensates for surge, swing, heave, pitch, roll and yaw.
In the German utility model not either is a method described for calculation of which control signals from said control system to the motors of said searchlight would be necessary to maintain said searchlights beam axis directed against a point in the sea. The utility model application is thus so rudimentary that the described method hardly may be performed in any adequate manner as it is presented without adding substantial elements, and thus would not be possible to perform for a person skilled in the art without adding substantial new elements. The method is also likewise described in a similar German patent.
To illustrate the disadvantages the German utility model presents, the calculation examples have been used. The results from the calculation examples are shown illustrated in FIG. 19-FIG. 31. A computer has been used to simulate how said vessel, searchlight, searchlight beam axis and said illuminated point on the surface of the sea moves over a calculation time span of 30 seconds.
Example 1 describes an imagined situation in which said vessel (1) is at rest at the position 60:00:00 N and 4:00:00 E. Said searchlight is arranged with at the centre of said boats length, 10 meters starboard for said boats longitudinal axis, and 8 meters above the sea level. An object is observed at a point (2p) 2.3″ E of said vessel (1), and said beam axis (3a) is arranged for intersecting with the water surface at the point (2p). Said vessel (1) has no translatory movements, it has no surge or swing movement, and has the following other movements: the pitch angle fluctuates between plus 5 degrees and minus five degrees, the roll angle fluctuates between plus 10 degrees and minus 10 degrees, and the yaw angle plus 4 degrees and minus 4 degrees. FIG. 19 shows said vessels (1) resulting movements represented by the parameters pitch, roll and yaw, FIG. 23 shows resulting computed angles (4a, 4b) of said beam axis, FIG. 24 show a vector coinciding and parallel with said beam axis (3a) in which said beam axis intersects with the water surface. This shows that an algorithm according to the German utility model in that respect will give a vector which points with a constant direction in space but which due to lack of parameters will move sideways with respect to the direction of said vector. FIG. 25 shows said vessels (1) position, defined by a cross, and the point where said beam axis (3a) intersects with the water surface according to what the German utility model may result in given our example.
The simulation illustrated in FIG. 24 shows that according to DE 20207444 the searchlight will be stabilised in pitch, roll and yaw and the direction of said beam axis (3a) will be maintained constant. On the other hand, according to the German utility model, deviations due to said searchlights (3) placement on said vessel (1), said searchlights (3) height over the water level or said searchlights (3) movement in space due to said vessels (1) pitch, roll yaw and heave movement are not computed. FIG. 25 shows that said beam axis (3a) according to the German utility model thus will not intersect with the water surface in the same point over a period of time and thus can not keep said beam axis (3a) directed towards the same stationary point (2p) in time. This rapid movement is unsuitable during searches.
Example 2 describes an imagined situation in which said vessel (1) begins in a point 60:00:00 N and 4:00:00 E. An object (2p) is observed at 2.3″ E of said vessel (1), and said beam axis (3a) is so directed as to intersect with the water surface in said point (2p). Said vessel (1) runs ahead with a speed of 6 knots, at the same time as the course is changed from 0 degrees to 30 degrees, so that the final position becomes 23 meters east and 88 meters north of the initial position. Said vessel has the following other movements: Pitch angle plus 5 degrees and minus 5 degrees, roll angle plus 10 degrees and minus 10 degrees and yaw angle plus 4 degrees and minus 4 degrees. FIG. 19 shows said vessels (1) movements in pitch, roll and yaw; FIG. 29 shows the calculated angles of said beam axis (4a, 4b). FIG. 30 shows a vector which is coincidental with and parallel to said beam axis (3a), in which its direction intersects with the water surface at a point. FIG. 31 shows said vessels (1) position, in which said vessels initial and final positions are given by crosses, and the point in which said beam axis (3a) intersects with the water surface.
The simulation illustrated in FIG. 30 shows that according to DE20207444 said searchlight will be stabilised in pitch, roll and yaw, and the direction of said beam axis (3a) will be maintained constant. However, according to the German utility model, no deviation due to said searchlights (3) placement on board said vessel, said searchlights (3) height above the water level, or said searchlights (3) movement in space due to said vessels (1) pitch, roll, yaw, and heave movement is calculated. FIG. 31 shows that said beam axis (3a), according to the German utility model, will not intersect with the water surface at the same point, and thus is not able to keep said beam axis (3a) directed towards the same point (2p). FIG. 31 clearly illustrates that said searchlight according to DE20207444 is little suitable to performing searches at sea, and that the intention of the invention can not be fulfilled such as the method is rudimentary described in the German utility model.
USD 327,953 is a design application showing a searchlight.
U.S. Pat. No. 650,574 describes a method for compensating for vertical sea induced movements during crane operations at sea, in which said method comprises measurements of the vessels pitch, heave and roll movements, for later to recalculate these movements to a from a crane hanging loads' vertical velocity from said vessel, until finally furnishing signals to a motor which is arranged for countering said vessels vertical movements by corresponding inverse movements. The patent does not however describe problems related to said cranes placement on board said vessel, and the technical solution described assumes that said crane is arranged in said boats mass centre. Any displacement of said cranes placement with respect to said boats mass centre will render the described calculations imprecise and thereby complicate the crane operations as described in the patent. Nor does the patent describe compensation for other spatial movements other than said vertical movement of said crane load, and thus will not be able to compensate for surge, sway and yaw movements, compensation of which is of vital importance to the present invention.
The background art is not able to solve the problem of directing a searchlight towards an object or a point in the sea, and maintain said illumination towards said point while the vessel bearing said searchlight simultaneously drives and performs rotational and translatory movements.